Blocking and fixing
Blocking
Add 250 µL of Assay Buer to each well and incubate at room
temperature for 2 hours. Alternatively the plate may be blocked over
night at 2°C to 8°C. Blocked plates can be stored at 2°C to 8°C for up to
one week.
Fixing
To store the coated plates for longer than one week aspirate Assay
Buer and add 150 µL Fixing Buer to each well. Incubate for 1 hour
at room temperature. Aspirate Fixing Buer and dry plates for 2 hours
at 37°C. When sealed with desiccant, the plates can be stored at 2°C to
8°C for 2 months.
Preparation of immunological reagents
Note: Centrifuge vials before opening to collect contents.
Preparation of standard
1. Reconstitute rat IL-4 standard protein with deionized or distilled
water. Reconstitution volume is indicated on the vial label (nal
concentration of reconstituted standard = 2 ng/mL). Allow the
standard to reconstitute for 10-30 minutes. Mix well prior to
making dilutions.
2. The concentrated rat IL-4 standard must be diluted 1:10 with
Assay Buer just prior to use in a clean plastic test tube according
to the following dilution scheme:
Reagents Volume
conc. Standard Protein (2 ng/mL) 23 µL
Assay Buffer 207 µL
Standard Protein (200 pg/mL) 230 µL
3. Shake gently to mix. After usage remaining diluted standard
cannot be stored and has to be discarded.
4. Aliquot the reconstituted concentrated standard and store at
-20°C.
Preparation of Biotin-Conjugate
Dilute concentrated Biotin-Conjugate 1:1000 with Assay Buer before
use. Use within 30 minutes after preparation. For one microwell plate
dilute the stock reagents as follows:
Reagents Volume
conc. Biotin-Conjugate 5.5 µL
Assay Buffer 5494.5 µL
Biotin-Conjugate 5.5 mL
Preparation of Streptavidin-HRP
Dilute concentrated Streptavidin-HRP 1:10,000 with Assay Buer
before use. Use within 30 minutes after preparation. For one microwell
plate dilute the stock reagents as follows:
Reagents Volume
conc. Streptavidin-HRP 1.1 µL
Assay Buffer 10,998.9 µL
Streptavidin-HRP 11.0 mL
Test protocol
1. Wash blocked or blocked and xed plates twice with
approximately 400 µL Wash Buer per well, with thorough
aspiration of microwell contents between washes. Allow the Wash
Buer to sit in the wells for about 10 – 15 seconds before
aspiration. Take care not to scratch the surface of the microwells.
After the last wash step, empty wells and tap microwell strips on
absorbent pad or paper towel to remove excess Wash Buer. Use
the microwell plate immediately after washing. Alternatively
microwell plate can be placed upside down on a wet absorbent
paper for no longer than 15 minutes. Do not allow wells to dry.
2. Add 100 µL Sample Diluent in duplicate all standard wells.
Pipee 100 µL of diluted standard (see “Preparation of
standard“ on page 2), (concentration = 200 pg/mL) in duplicate
into well A1 and A2. Mix the contents of wells A1 and A2 by
repeated aspiration and ejection (concentration of standard 1, S1 =
100 pg/mL), and transfer 100 µL to wells B1 and B2, respectively
(see Figure 1). Take care not to scratch the surface of the
microwells. Continue this procedure 5 times, creating two serially
diluted columns of rat IL-4 standard dilutions ranging from 100.0
to 1.60 pg/mL. Discard 100 µL from the last microwells (G1, G2).
Final volume in all wells is 100 µL.
Fig. 1 Dilute standards - microwell plate
3. Add 100 µL of Sample Diluent in duplicate to blank wells.
4. Add 50 µL of Sample Diluent to the sample wells.
5. Add 50 µL of each sample in duplicate to the sample wells.
6. Prepare Biotin-Conjugate (see “Preparation of Biotin-
Conjugate“ on page 2)
7. Add 50 µL of prepared Biotin-Conjugate to all wells.
8. Cover with an adhesive lm and incubate at room temperature
(18°C to 25°C) for 2 hours, on a microplate shaker if available.
9. Prepare Streptavidin-HRP (see “Preparation of Streptavidin-
HRP“ on page 2).
10. Remove adhesive lm and empty wells. Wash microwells 3 times
according to point a. of the test protocol. Proceed immediately to
the next step.
11. Add 100 µL of diluted Streptavidin-HRP to all wells, including
the blank wells.
12. Cover with an adhesive lm and incubate at room temperature
(18°C to 25°C) for 1 hour, on a microplate shaker if available.
13. Remove adhesive lm and empty wells. Wash microwells 3 times
according to point a. of the test protocol. Proceed immediately to
the next step.
14. Pipee 100 µL of Substrate Solution to all wells.
15. Incubate the microwell strips at room temperature (18°C to 25°C)
for about 10 minutes. Avoid direct exposure to intense light.
Monitor the color development on the plate. The substrate
reaction should be stopped (see next point of this protocol) before
positive wells are no longer properly recordable.
Determination of the ideal time period for color development has
to be done individually for each assay.
Add the stop solution when the highest standard has developed a
dark blue color. Alternatively the color development can be
monitored on a plate reader at 620 nm. The substrate reaction
should be stopped as soon as Standard 1 has reached an OD of 0.9
– 0.95.
2
Rat IL-4 Matched Pair User Guide